Put the mascarpone in the bowl of a food processor fitted with a metal blade and pulse until smooth. Scrape down the sides of the bowl with a rubber spatula and add the Worcestershire sauce, hot sauce, tomato paste, ketchup, horseradish, lemon zest and juice, salt and celery seeds. Process, scraping down the sides of the bowl as needed, until the dip is smooth, about 1 minute.
Transfer the dip to a serving bowl and serve with celery sticks for dipping.
Recipe courtesy of Giada De Laurentiis